Intermediate

These scopes offer higher performance and more advanced features than Level 1 Beginner models. They typically take a bit longer to learn and need some set-up or adjustments. But anyone with the slightest technical bent will have no problem getting familiar with these models. Referring to the manual is recommended.

Orion SkyQuest XT8g Computerized GoTo Dobsonian Telescope

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Orion Dobsonian telescopes have always been known for superb optical and mechanical quality, wonderful ease of use, and remarkably affordable prices. One other thing they - and almost all other Dobsonians on the market - have had in common: you pushed the telescope to your observing target by hand.

Until now. Orion is pleased to herald another giant leap in Dobsonian evolution with the introduction of the SkyQuest XTg series of fully motorized GoTo Dobsonian telescopes. Now, pointing an Orion Dobsonian to even the most elusive of NGC curiosities is as easy as pushing a button or two on the XTg Dobsonian telescope’s illuminated computerized GoTo hand controller. High-torque servo motors guided by two pairs of high-resolution encoders then slew the telescope right to your object of interest - any of over 42,000 objects in the computerized GoTo controller’s database. No more nudging the telescope tube continuously to keep the object from drifting out of the field of view, either. The 8” aperture XT8g Dobsonian automatically tracks the celestial object’s apparent motion, keeping it centered in the telescope eyepiece while you savor the view. Any amateur astronomer who has ever manually tracked a night-sky object with a Dobsonian telescope will greatly appreciate the benefit of this convenient and precise tracking system. What’s more, the closed-loop electronics of the XT8g let you move the telescope manually - or endure the accidental bump - without losing orientation for accurate, automated GoTo pointing!

The Orion SkyQuest XT8g Dobsonian telescope combines GoTo pointing convenience with excellent portability and an affordable price. It features a 203mm (8") aperture; 1200mm focal-length parabolic mirror (f/5.9) made from low-thermal-expansion optical glass, with enhanced reflectivity (94%) aluminum coatings for high-definition images. The mirror is center marked to make alignment of the optics (also called collimation) easier and more precise. The optical tube comes equipped with an accurate dual-speed 2" Crayford focuser complete with an 1.25" adapter for use with both 2” and 1.25” telescope eyepieces. The 11:1 fine focus knob ensures that you’ll quickly find that ultra-sharp focus point that makes your target object pop with dazzling clarity! The telescope’s modern open mirror cell design facilitates efficient cooling of the primary mirror to ambient temperature so you can spend more time viewing, and less time waiting for temperature equilibration. The mirror cell also features threaded holes for mounting an optional cooling accelerator fan, for even faster equilibration.

The GoTo Dobsonian base of the SkyQuest XT8g comes with all optical encoders, drive motors, and gears pre-installed, making assembly a breeze. The telescope optical tube drops into the GoTo base on a dovetail trunnion and conveniently locks in place with a single hand knob. A simple two-star alignment procedure is all it takes to orient the telescope to the sky for GoTo operation. Then let the fun begin! When you’re ready to call it a night, just loosen the knob and pop the optical tube off the Dobsonian base for easy transport or storage. Handles on the base’s front and side panels make it easy to lift and carry.

A thorough set of standard accessories packaged with the XT8g Dobsonian telescope include an Orion EZ Finder II reflex sight, removable eyepiece rack with holes for one 2" and three 1.25" telescope eyepieces, hand controller mounting bracket, quick collimation cap, a wide-field 28mm DeepView 2" eyepiece, and a 12.5mm illuminated-crosshair Plossl eyepiece (1.25") which enables ultra-precise GoTo system alignment. The XT8g drive motors require power from a 12-volt DC field battery or AC adapter, sold separately. A DC cable is included with telescope that has an auto-lighter style plug on one end for connecting to your 12-volt DC power source, and a coaxial plug on the other end that fits the power jack installed on the Dobsonian base.

You’re going to love plying the night skies with the SkyQuest XT8g GoTo Dobsonian telescope. The computerized GoTo hand controller’s softly red-illuminated keypad lets you select an object from a variety of intuitive menus, or take a tour of the best objects in the sky at any time of year. The time you’ll save by not having to manually search for your targets will allow you to kick back, relax, and spend more time enjoying the magnificent views through the eyepiece.

If you are an intermediate or avid deep-sky hunter who wants a big-aperture telescope but not the high price tag, a Dobsonian is the way to go. And now, finally, you can have one that offers the convenience of motor driven GoTo pointing - to anything in the heavens you’d like to see! Make your next telescope the Orion SkyQuest XT8g GoTo Dobsonian!

Limited Warranty against defects in materials or workmanship for one year from date of purchase. This warranty is for the benefit of the original retail purchaser only. For complete warranty details contact us at 800-676-1343.

Warning

Please note this product was not designed or intended by the manufacturer for use by a child 12 years of age or younger.

User level

Level 1 Beginner - Suited for a wide range of uses, these telescopes are simple to operate and set up. Some initial assembly may be required. Very good optical and mechanical quality. Great for families, young people, and folks who don't want to mess with equipment but just want to take a look. Any of these scopes will show you countless lunar craters, Saturn's rings and a myriad of star clusters and nebulas! Referring to the manual is recommended.

Level 2 Intermediate - These scopes offer higher performance and more advanced features than Level 1: Beginner models. They typically take a bit longer to learn and need some set-up or adjustments. But anyone with the slightest technical bent will have no problem getting familiar with these models. Referring to the manual is recommended.

Level 3 Advanced - These scopes provide the best performance but may require more skill to master and appreciate. They have exceptionally fine optics and mechanics. Some are easy to use but are but on the large or heavy side. Some are intended for specialized uses. These scopes will appeal to the more technically inclined. Referring to the manual is highly recommended.

Level 4 Expert - Expert telescopes offer uncompromising optical and mechanical quality for the most demanding amateur astronomer. They may be technically involved or designed for specialized use, such as astrophotography or detailed deep sky observation. They carry a premium price, but are designed to provide the ultimate performance in the field. Referring to the manual is highly recommended.

Optical design

Reflector telescopes use a pair of large and small mirrors to direct incoming light to the eyepiece.
Refractor telescopes refract, or "bend" incoming light to a focus by means of an objective lens.
Cassegrain telescopes, such as Maksutov-Cassegrains, "fold" incoming light using two mirrors and a front "corrector" lens.

Optical diameter

For telescopes, the optical diameter (also known as aperture) is the size of a telescope's main light-collecting lens or primary mirror, measured in millimeters or inches. Telescopes with larger optical diameters collect more light, which leads to an increase in brightness and image resolution compared to smaller instruments.

For binoculars, the optical diameter (also known as objective lens diameter) is the size of each of the front-facing objective lenses of a binocular measured in millimeters. Binoculars with larger objective lenses collect more light, which increases image resolution and brightness. Binoculars with larger objective lenses are recommended for low light situations, and binoculars with at least 50mm or larger objective lenses are recommended for pleasing astronomical observations at night.

Focal length

The distance from the center of a curved mirror or lens at which parallel light rays converge to a single point. The focal length is an inherent specification of a mirror or lens and is one of the factors in determining resultant magnification for a telescope (along with the focal length of the eyepiece being used).

Focal ratio

The focal ratio of an optical system is the ratio of a telescope's focal length to its aperture. Short focal ratios (f/5, f/4.5) produce wide fields of view and small image scales, while long focal lengths produce narrower fields of views and larger image scales.

Optics type

Newtonian reflectors will have either a spherical shaped mirror, which is less expensive to produce, or a higher quality parabola, which does not result in spherical aberration. Cassegrain telescopes routinely use spheres in addition to other lenses in the optical path to correct for residual spherical aberration.
Refractors use a series of lenses to provide a clear image. Designs range from a standard air-spaced doublet (two lenses in a row) to exotic designs such as oil-spaced triplets and 4-element multi group lenses.

Glass material

Refractors use glass lenses to focus the light, and the glass material plays an important role in the quality of the resulting image. Standard achromatic refractors routinely use Crown and Flint for the two elements, but more expensive apochromatic refractors can use ED (extra low dispersion) glass for one or more of the lenses. Reflector mirrors are made from glass with different levels of thermal expansion. Standard mirrors are made from material such as Soda-Lime Plate glass and BK-7 glass. Glass with Pyrex or other low thermal expansion material will not change shape as dramatically during the cool-down period, resulting in more stable images during this period.

Resolving power

The theoretical resolving power of a telescope can be calculated with the following formula: Resolving power (in arc seconds) = 4.56 divided by aperture of telescope (in inches). In metric units, this is: Resolving power (in arc seconds) = 116 divided by aperture of telescope (in millimeters). Note that the formula is independent of the telescope type or model, and is based only upon the aperture of the telescope. So the larger the telescope's aperture, the more it is capable of resolving. This is important to keep in mind when observing astronomical objects which require high resolution for best viewing, such as planets and double stars. However, it is usually atmospheric seeing conditions (not the telescope) which limits the actual resolving power on a given night; rarely is resolution less than one arc-second possible from even the best viewing locations on Earth.

Lowest useful magnification

Lowest useful magnification is the power at which the exit pupil becomes 7mm in diameter. Powers below this can still be reached with the telescope to give wider fields of view, but the image no longer becomes brighter at a lower power. This is due to the fact that the exit pupil of the telescope (the beam of light exiting the eyepiece) is now larger than the average person's dark adapted pupil, and no more light can fit into the eye.

Highest useful magnification

The highest practical limit is different from the often used "highest theoretical magnification" specification. The "theoretical" limit generally is 50x the aperture of the scope in inches (2x the aperture in mm). So for example, an 80mm refractor is capable of 160x, and a 10" telescope is theoretically capable of 500x magnification.
But after approximately 300x, theory breaks down and real world problems take over. The atmosphere above us is constantly in motion, and it will distort the image seen through the telescope. This effect may not be noticeable at lower powers, but at higher powers the atmosphere will dramatically blur the object, reducing the quality of the image. On a good night (a night where the air above is steady and the stars aren't twinkling), the practical upper limit of a large telescope is 300x, even thought the theoretical limit may be much higher. This doesn't mean the scope will never be able to reach those higher "theoretical" powers - there will be that rare night where the atmosphere is perfectly still and the scope can be pushed past it's practical limit, but those nights will be few and far between.

Astro-imaging capability

The astro-photographic capability of the telescope is based on the style, stability, and accuracy of the mount and tripod. Telescopes on either very lightweight mounts or non tracking mounts (such as Dobsonians) are capable of only very short exposures such as lunar photographs. If a motor drive is attached to an equatorial mount, even a small lightweight mount is capable of capturing some planetary detail. Larger EQ mounts that utilize very precise tracking and excellent stability are capable of longer exposure deep-sky photography.

Motor drive compatibility

A motor drive automatically moves the telescope in right ascension at the same rate as the east-west drift of the stars so stars can be continuously tracked in the eyepiece without manual adjustment. Motor drives are usually equipped with a hand control that allows the telescope's tracking speed to be slightly increased or decreased, which is particularly critical when taking long-exposure astro-images.

Computerized compatibility

Some mounts are compatible with a motorized Go-To system for fully automated computer finding of objects in the night sky. Others mounts are compatible with computer finding systems which require the user to manually move the mount to the object's position as indicated by the computer finder.

Warranty

This warranty gives you specific legal rights. It is not intended to remove or restrict your other legal rights under applicable local consumer law; your state or national statutory consumer rights governing the sale of consumer goods remain fully applicable.

Orders received by 1pm Eastern Time for in-stock items ship the same business day. Orders received after 1pm will ship the next business day. When an item is not in-stock we will ship it as soon as it becomes available. Typically in-stock items will ship first and backordered items will follow as soon as they are available. You have the option in check out to request that your order ship complete, if you'd prefer.

A per-item shipping charge (in addition to the standard shipping and handling charge) applies to this product due to its size and weight. This charge varies based on the shipping method.

At Orion, we are committed to sharing our knowledge and passion for astronomy and astrophotography with the amateur astronomy community. Visit the Orion Community Center for in-depth information on telescopes, binoculars, and astrophotography. You can find astrophotography "how to" tips and share your best astronomy pictures here. Submit astronomy articles, events, and reviews, and even become a featured Orion customer!